OK, this is really long, you have to be a serious number geek to call this fun.
I’ve been hard core “gotta have a Harvester for towing”, but some recent threads have me reevaluating. The charging infrastructure is not there today for what we do, but might it be there in three years when we take delivery? I’ve tried to make reasonable projections of energy use from what we know about the BEV and Harvester plus about towing with other EVs. I’m not an EV owner but I’ve been doing a lot of research in the past few months. Corrections to reasoning or math are greatly appreciated.
For normal folks here is a summary. I’m assuming road tripping a BEV keeping the battery between 20% and 80%. This gives BEV recharge stops at 210 miles not towing and 105 miles towing, taking 30 minutes at a slower DCFC (150 kW) and 15 minutes at a faster DCFC (300 kW). I’m assuming road tripping a Harvester using gas to keep the battery between 40% and 60%, refilling when the gas tank gets down to 1/4. All the math is below, but this gives gas stops at 262 miles when not towing and 131 miles when towing.
Since we aim for 300 mile towing days this says we would need 3 recharging stops per day with the BEV, taking a total of 45 to 90 minutes. Still a big uncertainty about areas where DCFC stops are more than 100 miles apart. The next three years will be interesting.
I’m using the Ike Gauntlet as the extreme uphill benchmark and assuming 1 mi/kWh not towing and 0.5 towing. The BEV would use 6.4% of the battery when not towing and 12.8% towing for the uphill portion. The Harvester would use 12.3% of the battery not towing and 24.6% towing. This assumes the Harvester is just using the battery for those 8 miles. The generator will contribute some of course, but this makes the math easier and shows that keeping the battery generally above 40% should be fine.
For those wondering about the effects of speed, I can’t guess what it means in terms of mi/kWh. But aerodynamic drag increases 40% going from 55 mph to 65, and 33% going from 65 to 75. And they multiply, not add, it is 86% going from 55 to 75.
Stop reading now unless you are weird.
To set the stage a lot of EVs with similar size and shape seem to get around 2.5 mi/kWh in general use and half that overall when towing. I found a thread on a Rivian forum where someone with a Gen 1 quad motor R1T towed a 20’ Airstream Basecamp (GTW 4300 lbs) from Cupertino to Yellowstone, the Tetons, and back getting 1.3 mi/kWh on the way out and 1.2 on the return. Edmunds has a YouTube video about towing a 7500 lb box trailer in a SoCal loop from Santa Clarita to Bakersfield, Mojave, and back with an R1T and F-150 Lightning getting 1 mi/kWh overall. TFL has done some Ike Gauntlets towing 9000 lbs with a Gen 1 quad motor R1T, F-150 Lightning, and Silverado EV getting just under 0.4 mi/kWh on the uphill portion.
In the Motor Trend interview Scott Keogh said around 120 to 130 kWh for the BEV battery and around 60 to 70 for the Harvester. I’ll use 125 and 65. For the BEV a 350 mile range is an average of 2.8 mi/kWh. For the Harvester a 150 mile electric range is an average of 2.3 mi/kWh. Those are when not towing, so 1.4 and 1.15 when towing. I’m arbitrarily using 65 mph in calculations needing a speed. And when converting kW to hp I’m just doing a straight energy conversion, not accounting for conversion losses or ICE efficiency.
For the Harvester 350 miles with 15 gallons of gas is an average of 23.3 mpg when not towing, 11.7 when towing. From another angle, 350 miles at 2.3 mi/kWh is 152 kWh not towing, and the same 152 kWh for 175 miles at 1.15 mi/kWh when towing. Towing or not this is 10.1 kWh/gal. At 65 mph 350 miles takes 5.4 hours, so an average of 28 kW from the generator when not towing, which converts to 38 hp. At 65 mph 175 miles takes 2.7 hours, so an average of 56 kW from the generator when towing, which converts to 76 hp.
I’m assuming towing days of at least 300 miles, so there will be mid day stops. For the BEV I’m assuming driving down to 20% then recharging to 80%, so using 60% between stops. For simplicity I’m assuming starting a day at 80%. I’m assuming BEV and Harvester need to climb the Ike and have at least 10% battery at the top. The BEV estimates are simple calculations using kW and miles. I’m assuming an older DCFC will deliver 150 kW and a newer one 300. To keep things simple for the Harvester I’m looking at just gas use, not trying to optimize a mix of battery and gas. The generator would run as needed to keep the battery in some reasonable range like 40-60%. Of course possibly dipping below 40% to climb the Ike. I’m assuming the gas tank starts full, drive to 1/4 then refill.
For the BEV 60% of the battery is 75 kWh, at 2.8 or 1.4 mi/kWh giving 210 miles between stops not towing and 105 towing, taking 30 minutes at a slower DCFC and 15 minutes at a faster one. For the Harvester 3/4 of the 15 gallon tank is 11.25 gallons, at 10.1 kWh/gal this gives 114 kWh. Not towing at 2.3 mi/kWh you drive 262 miles between gas stops, towing it is 131 miles.
If we assume the uphill portion of the Ike doubles energy use this gives the BEV 1.4 mi/kWh not towing and 0.7 mi when towing. For the Harvester this is 1.15 mi/kWh when not towing and 0.6 mi/kWh when towing. To be more inline with the TFL numbers I’m using 1.0 and 0.5 mi/kWh for both vehicles. The uphill portion is 8 miles, so 8 kWh when not towing and 16 kWh when towing. This is 6.4% not towing and 12.8% towing for the BEV battery, so being at least at 20% at the bottom should be fine. This is 12.3% and 24.6% of the Harvester battery, so being at least at 40% the bottom should be fine.
I’ve been hard core “gotta have a Harvester for towing”, but some recent threads have me reevaluating. The charging infrastructure is not there today for what we do, but might it be there in three years when we take delivery? I’ve tried to make reasonable projections of energy use from what we know about the BEV and Harvester plus about towing with other EVs. I’m not an EV owner but I’ve been doing a lot of research in the past few months. Corrections to reasoning or math are greatly appreciated.
For normal folks here is a summary. I’m assuming road tripping a BEV keeping the battery between 20% and 80%. This gives BEV recharge stops at 210 miles not towing and 105 miles towing, taking 30 minutes at a slower DCFC (150 kW) and 15 minutes at a faster DCFC (300 kW). I’m assuming road tripping a Harvester using gas to keep the battery between 40% and 60%, refilling when the gas tank gets down to 1/4. All the math is below, but this gives gas stops at 262 miles when not towing and 131 miles when towing.
Since we aim for 300 mile towing days this says we would need 3 recharging stops per day with the BEV, taking a total of 45 to 90 minutes. Still a big uncertainty about areas where DCFC stops are more than 100 miles apart. The next three years will be interesting.
I’m using the Ike Gauntlet as the extreme uphill benchmark and assuming 1 mi/kWh not towing and 0.5 towing. The BEV would use 6.4% of the battery when not towing and 12.8% towing for the uphill portion. The Harvester would use 12.3% of the battery not towing and 24.6% towing. This assumes the Harvester is just using the battery for those 8 miles. The generator will contribute some of course, but this makes the math easier and shows that keeping the battery generally above 40% should be fine.
For those wondering about the effects of speed, I can’t guess what it means in terms of mi/kWh. But aerodynamic drag increases 40% going from 55 mph to 65, and 33% going from 65 to 75. And they multiply, not add, it is 86% going from 55 to 75.
Stop reading now unless you are weird.
To set the stage a lot of EVs with similar size and shape seem to get around 2.5 mi/kWh in general use and half that overall when towing. I found a thread on a Rivian forum where someone with a Gen 1 quad motor R1T towed a 20’ Airstream Basecamp (GTW 4300 lbs) from Cupertino to Yellowstone, the Tetons, and back getting 1.3 mi/kWh on the way out and 1.2 on the return. Edmunds has a YouTube video about towing a 7500 lb box trailer in a SoCal loop from Santa Clarita to Bakersfield, Mojave, and back with an R1T and F-150 Lightning getting 1 mi/kWh overall. TFL has done some Ike Gauntlets towing 9000 lbs with a Gen 1 quad motor R1T, F-150 Lightning, and Silverado EV getting just under 0.4 mi/kWh on the uphill portion.
In the Motor Trend interview Scott Keogh said around 120 to 130 kWh for the BEV battery and around 60 to 70 for the Harvester. I’ll use 125 and 65. For the BEV a 350 mile range is an average of 2.8 mi/kWh. For the Harvester a 150 mile electric range is an average of 2.3 mi/kWh. Those are when not towing, so 1.4 and 1.15 when towing. I’m arbitrarily using 65 mph in calculations needing a speed. And when converting kW to hp I’m just doing a straight energy conversion, not accounting for conversion losses or ICE efficiency.
For the Harvester 350 miles with 15 gallons of gas is an average of 23.3 mpg when not towing, 11.7 when towing. From another angle, 350 miles at 2.3 mi/kWh is 152 kWh not towing, and the same 152 kWh for 175 miles at 1.15 mi/kWh when towing. Towing or not this is 10.1 kWh/gal. At 65 mph 350 miles takes 5.4 hours, so an average of 28 kW from the generator when not towing, which converts to 38 hp. At 65 mph 175 miles takes 2.7 hours, so an average of 56 kW from the generator when towing, which converts to 76 hp.
I’m assuming towing days of at least 300 miles, so there will be mid day stops. For the BEV I’m assuming driving down to 20% then recharging to 80%, so using 60% between stops. For simplicity I’m assuming starting a day at 80%. I’m assuming BEV and Harvester need to climb the Ike and have at least 10% battery at the top. The BEV estimates are simple calculations using kW and miles. I’m assuming an older DCFC will deliver 150 kW and a newer one 300. To keep things simple for the Harvester I’m looking at just gas use, not trying to optimize a mix of battery and gas. The generator would run as needed to keep the battery in some reasonable range like 40-60%. Of course possibly dipping below 40% to climb the Ike. I’m assuming the gas tank starts full, drive to 1/4 then refill.
For the BEV 60% of the battery is 75 kWh, at 2.8 or 1.4 mi/kWh giving 210 miles between stops not towing and 105 towing, taking 30 minutes at a slower DCFC and 15 minutes at a faster one. For the Harvester 3/4 of the 15 gallon tank is 11.25 gallons, at 10.1 kWh/gal this gives 114 kWh. Not towing at 2.3 mi/kWh you drive 262 miles between gas stops, towing it is 131 miles.
If we assume the uphill portion of the Ike doubles energy use this gives the BEV 1.4 mi/kWh not towing and 0.7 mi when towing. For the Harvester this is 1.15 mi/kWh when not towing and 0.6 mi/kWh when towing. To be more inline with the TFL numbers I’m using 1.0 and 0.5 mi/kWh for both vehicles. The uphill portion is 8 miles, so 8 kWh when not towing and 16 kWh when towing. This is 6.4% not towing and 12.8% towing for the BEV battery, so being at least at 20% at the bottom should be fine. This is 12.3% and 24.6% of the Harvester battery, so being at least at 40% the bottom should be fine.
